Hi,
This is a follow-up on the situation I had with a 4 TB SATA raid unit based on an Accusys ACS-8960 SATA-fibre RAID Kit, connected to a Qlogic 2312 fibre channel hba. I was getting all kinds of read/write errors, and was not able to reliably create and mount file systems. Actually, there were errors, regardless of whether the unit was connected to Windows, 32-bit Linux, or 64-bit linux, it's just that 64-bit linux was more verbose about reporting errors, so it seemed worse. This shows that the problem was not in the Qlogic driver.
It turns out that there are internal bugs or limitations in the RAID firmware that generates severe errors if you set up a raid array with more than 1TB. In the case of 250GB SATA drives, that means no more than 5 drives in an array. Since there are 16 drives in the physical unit, I needed to set up 3 arrays, and leave 1 drive idle. This yields a total usable capacity of 2.7TB, split into 3 devices.
OK, now back to the question of Logical Volume Management. I tried again to put all the devices into a single logical volume, but LVM would not create a LV greater than 2 TB. I made sure to set up the physical volumes with large physical extents (128 MB) which ought to make it possible to create LVs up to 16TB, but still it does not work.
The SuSE white paper on LVM says that 2TB is only a limitation for 32 bit hardware. Could it be that settings which limit it to 2TB were included to allow backward compatibility with 32 bit libraries and applications? Can I change some parameters to remove that limitation?
Thanks, John Craig